Noise barriers play a crucial role in mitigating railway noise, with the aerodynamic pressure exerted by passing trains being a key factor in their structural design, particularly for those installed along high-speed railways. While previous studies have focused on the effects of train speed, geometry, and distance from the track centre, and have developed models incorporating these factors, limited attention has been given to the impact of bilateral layouts and barrier height on this pressure. Quantitative assessments of these two factors remain scarce, and existing pressure calculation models inadequately address their influence. This study addressed these gaps by employing computational fluid dynamics (CFD) simulations, validated by field test data, to qualitatively and quantitatively analyze the effects of barrier layout and height on the aerodynamic pressure acting on vertical noise barriers. The results demonstrate that two distinct transient pressure fluctuations over time are generated by the train’s nose and tail, in agreement with the findings of the field tests. A bilateral layout increases peak pressure by up to 8.5%, particularly as the distance to the train centreline decreases. Moreover, increasing barrier height from 2 to 4 m resulted in a maximum pressure amplification of 13.23%, though the amplification rate diminished with further height increases. To address the limitations of existing pressure calculation models, an exponential model was developed to account for the amplification effect of bilateral layouts, while a logarithmic correction factor was introduced to account for barrier height. These models were integrated into a comprehensive aerodynamic pressure calculation framework, effectively capturing the combined impacts of barrier layout and height. Validated through simulations, the proposed model offers a more accurate and practical approach for predicting train-induced aerodynamic pressure on noise barriers, providing valuable insights to inform their structural design.

Railway noise barriers are an essential piece of infrastructure for reducing noise propagation. However, these barriers experience aerodynamic loads generated by high-speed trains, leading to dynamic effects that may compromise their fatigue capacity. The most common structural design for railway noise barriers consists of vertical configurations of posts and panels. However, there have been few dynamic analyses of steel post/wood panel noise barriers under train-induced aerodynamic loads. This study used dynamic finite element analysis to assess the dynamic behavior of such noise barriers. Analysis of a 40-m-long noise barrier model and a triangular simplified load model, the latter of which effectively represented the detailed aerodynamic load, were first used to establish the model and input of the moving load during dynamic simulation. Then, the effects of different parameters on the dynamic response of the noise barrier were evaluated, including the damping ratio, the profile of the steel post, the span length of the panel, the barrier height, and the train speed. Gray relational analysis indicated that barrier height exhibited the highest correlations with the dynamic responses, followed by train speed, post profile, span length, and damping ratio. A reduction in the natural frequency and an increase in the train speed result in a higher peak response and more pronounced fluctuations between the nose and tail waves. The dynamic amplification factor (DAF) was found to be related to both the natural frequency and train speed. A model was proposed showing that the DAF significantly increases as the square of the natural frequency decreases and the cube of the train speed rises.

Rapporten diskuterar tidsberoende deformationer i anläggningskonstruktioner av armerad betong. Deformationerna kan bero på faktorer som uttorkning och fuktförhållanden (krympning) och/eller laster (krypning). I två bilagor ges en presentation av metoder för modellering (Bilaga 1) och av beräkning av spännkraftförluster i spännarmering (Bilaga 2). Områden för fortsatta studier rekommenderas.

The report discusses time-dependent deformations in civil engineering structures made of concrete. These deformations can depend on factors such as drying and moisture conditions (shrinkage) and/or loads (creep). Two appendices provide state-of- the-art reports  on modelling (Appendix 1) and on prestress losses in reinforcement (Appendix 2). Further studies are recommended.

Reinforced concrete (RC) trough bridges form a crucial part of Europe's railway infrastructure. These structures consist of a U-shaped cross-section (two longitudinal beams and a slab) designed to accommodate the ballast. For the case of the Iron Ore Line, a critical corridor located in the north of the country, RC trough bridges represent about 40 % of the railway bridge population. Many of these bridges have surpassed 50 years of service, enduring over 10 million cycles of fatigue loading, with increases of axle loads since their construction due to demands associated with the iron ore extraction and transportation. As these structures approach critical maintenance or replacement decisions, understanding their long-term performance and remaining capacity is essential. This study experimentally investigates the degradation behavior of a full-scale RC trough bridge subjected to progressive cyclic loading, simulating fatigue effects over time. During the controlled laboratory tests, the overall performance of the bridge is assessed, focusing on the stiffness loss of slab and beams, cracking, and force redistribution. Fatigue verifications based on Eurocode EN1992–1–1 and fib Model Code 2020 are performed alongside the reliability analysis using the First-Order Reliability Method (FORM) to evaluate structural safety levels. While fatigue damage is evident in the slab's tensile zone, the overall structural response indicates that the bridge maintains its functional capacity after simulating 48 years of service. However, the code-based reliability analysis indicates lower-than-target reliability levels for reinforcement, suggesting a conservative estimation of reinforcement capacity to withstand cyclic loading.

This paper investigates the current landscape of multiscale studies in concrete composites incorporating molecular dynamics (MD) methods. Through a thorough literature analysis, it was determined that finite element, discrete element, homogenization, microphysical characterization, and machine learning methods are better suited for integration with MD in multiscale studies of concrete composites. The paper delves into MD's application characteristics and the selection of force fields in multiscale studies and provides a summary of the combined applications between MD and various methods. Challenges identified include the optimization of MD simulations and the appropriate selection of combined methods. The conclusions underscore the growing recognition of MD's significance, advocating for rational multi-method integration in multiscale approaches to effectively advance research on concrete composites.

Fatigue significantly impacts engineering structures, especially reinforced concrete, which endures millions of cyclic loads over its service life. Understanding the progressive degradation of concrete’s mechanical properties under fatigue is critical. This paper reviews existing degradation models, encompassing stiffness degradation, strength degradation, and strain development models. Then, these models are compared in terms of accuracy and applicability, and potential research directions for concrete damage modeling under fatigue are proposed. This work aims to serve as a valuable resource for future investigations and engineering applications. 

With increasing traffic volumes on Malmbanan (the Ore Line) between the ore fields in Northern Sweden and the harbors in Luleå and Narvik, there is a need to raise the axle load allowed on the track, This, in turn, necessitates the analysis and if needed, enhancement of the capacity of the railway bridges.

To facilitate this, fatigue tests are being conducted on a full-scale model of a reinforced concrete trough bridge. Calculations of the load effects from dead weight and axle loads are performed using the Eurocodes and the fib Model Codes (2010 and 2020).

The results indicate that the axle load on the Ore line can be increased to 35 tons without the risk of bending or shear fatigue failure in the trough bridges. However, the fatigue capacity varies considerably, both between different bridges and across different codes, so continued Structural Health Monitoring is recommended.

Corrosion of steel reinforcement in concrete is a significant cause of structural failure, particularly in environments exposed to chloride ions and mechanical stress. The passivation film on steel reinforcement, composed of hematite or magnetite, plays a crucial role in protecting the steel from further corrosion. However, the intrusion of harmful ions or mechanical stress can compromise the film’s integrity, transforming it into a loose structure and accelerating the corrosion process, leading to structural failure. This study investigates the mechanical behaviors at the interfaces between corrosion products (hematite and magnetite) and C-S-H using reactive molecular dynamics. C-S-H and interfacial models incorporating hematite and magnetite were developed, with stress–strain analysis refined by filtering raw data and using true strain rather than engineering strain to improve the precision of the stress–strain responses. The results indicate that the Magnetite-CSH interface is more prone to loosening under external forces compared to the Hematite-CSH interface, thereby reducing its corrosion resistance. Structural evolution analysis under uniaxial tension highlights the detrimental effects of passivation film degradation on interfacial mechanical properties. This study contributes to improving the precision of stress–strain responses in MD models and facilitates comparison of mechanical properties at the nanoscale with results from other scales. The findings provide valuable guidance for improving the durability and performance of construction materials in corrosive environments, helping to bridge the gap between molecular-level simulations and macroscopic experimental data.

A carefully studied evaluation was necessary to replace an existing pre-stressed concrete box girder bridge that had been in service for over 60 years, in Kalix, Northern Sweden. The bridge was 283.6 m long divided into five spans, and it was constructed using the balanced cantilever method. The decision to replace the old bridge created the need to evaluate a demolition procedure for it, one carefully designed not only to avoid damaging the newly built bridge or creating stability-related issues, but also to prevent any debris from falling into the Kalix River, which is part of a Natura 2000 protected area. This article focuses on the comprehensive methodology, on the demolition design, and on the observations related to residual prestress levels in the bridge, indirectly obtained through a reversed-engineering FEM process and on the limitations of the demolition technology to be used in these specific cases. Several variables were monitored during the deconstruction process, to control the structural stability better during all the phases of the project. The main outcome of the full condition assessment is that it provides the information needed to make informed decisions for interventions on these types of structures.

This study utilized molecular dynamics simulations to investigate the shear behaviour of the interface between new and old concrete. Two atomic models were developed to represent the new- to-old concrete interface, using hydrated calcium silicate (CSH) substrates with different water-to- silica ratios: CSH1 (H₂O/Si=1.0)-to-CSH3 (H₂O/Si=1.68) and CSH2 (H₂O/Si=1.5)-to-CSH3 interfaces. The results show that the primary bonding type in both interfaces is the Ca-O bond, and shear failure predominantly occurs within the CSH3 substrate with lower strength and unstable bond energy. Furthermore, the shear strength of the CSH1-to-CSH3 interface (0.93GPa) is 34.8% higher than that of the CSH2-to-CSH3 interface, indicating a correlation between shear property and bond energy stability and strength of the substrate. This study provides theoretical support for the design and optimization of new-to-old concrete interface.